494 



SCIENCE 



[N. S. Vol. XXXIII. No. 848 



Examination of the first volume gives quite 

 a different conception of the field of human 

 embryology from that obtained from other 

 older text-books on the subject; for instance, 

 Minot's very successful and constructive text- 

 book of twenty years ago. It was evident then 

 that, though much valuable work had already 

 been done in various lines, it was still of a 

 scattered character and unorganized. The 

 effect, as a whole, was inconclusive. There 

 were very few topics which had been studied 

 with thoroughness or on sufiicient human ma- 

 terial. 



In the new book we find that a considerable 

 mass of fresh facts and accurate information 

 have been accumulated, from intensive and 

 systematic studies of a far more complete 

 series of embryos, by more effective methods. 

 Though much remains to be done in every 

 department of investigation, it is now clear 

 that the study of human embryos has be- 

 come organized. Extensive collections are 

 accessible. There is a systematic effort to ob- 

 tain more complete records in every chapter 

 of the history. The comparative and experi- 

 mental method is not less used, but has be- 

 come more an aid to interpretation; while the 

 results secured from the study of human ma- 

 terial itself now overshadow all else. 



Another striking feature of the new book 

 is the fact that it is the product of a coopera- 

 tion between so many active American anato- 

 mists with well-known Germans; and that it 

 is published, at the same time, in two lan- 

 guages. This is not only a recognition of the 

 extent of His's infiuence, and of the general 

 wide growth of a cooperative spirit in scien- 

 tific anatomical research, which has become 

 very marked in this science; it is also a sub- 

 stantial appreciation from abroad of the effect- 

 ive work which has been done in embryology 

 among our anatomists in recent years. Al- 

 most every chapter of the book enforces this 

 fact, and the use of illustrations and refer- 

 ences to contributions from Americans pub- 

 lished in the American Journal of Anatomy 

 is frequent. Nine of the fifteen editors are 

 Americans and, of these, five are pupils of 



Dr. Mall, whose initiative and stimulating ex- 

 ample have encouraged much of the activity 

 in embryological investigations of this char- 

 acter in this country. 



Keibel writes the more general chapters in 

 the first part (90 pages), including the his- 

 torical introduction, the account of the germ- 

 cells, fertilization, segmentation, young hu- 

 man ova, germ-layers and gastrulation, and a 

 general summary of the development of the 

 embryo. The rather restricted space given to 

 these topics, which are treated so extensively 

 in Hertwig's " Handbook of Comparative 

 Embryology," is an illustration of the limita- 

 tion of the scope of the new work to the re- 

 sults of the study of human material. Much 

 of the greatest interest connected with these 

 topics is here necessarily omitted, but there is 

 a decided advantage in exhibiting the actual 

 status of our knowledge. All through these 

 chapters Keibel's fine critical judgment is evi- 

 dent. One receives the true impression that 

 the writer has thorough personal familiarity 

 with the facts. Nowhere is a nice judicial 

 decision in such demand as in discussions 

 about young human ova, hence we are espe- 

 cially glad to find this chapter by Keibel, 

 whose treatment is masterful and illumina- 

 ting. The tables are new and the details of 

 comparison of young stages are satisfactory. 

 The reader has an opportunity to secure a 

 necessary amount of detail often lacking, 

 confused or pointless in other accounts. The 

 obstetrician will find much of interest here. 

 Keibel's discussion of germ-layers is espe- 

 cially well put. The summary and resume of 

 the general history of the embryo based on 

 the His and Keibel-Elze Nommentafeln of 

 human embryos is excellent, the little critical 

 accounts of each important embryo being 

 well worth while. 



Grosser's long chapter (90 pages) on men- 

 struation, implantation, placentation, mem- 

 branes, etc., is based on extensive personal in- 

 vestigations. This account is almost a 

 monographic treatment of these subjects. 

 The obstetrician will find a mine of discov- 

 eries in this chapter and the two following 

 ones. The trophoblast, chorion, villi, decidua, 



